The present invention relates to a spindle motor capable of operating at a high rotational speed, and a magnetic disk drive capable of transferring data at a high data transfer rate.
Clients require a magnetic disk drive for use in a server to operate at a high data transfer rate. A disk needs to be rotated at a high rotational speed to meet such a requirement. A bearing mechanism according to an invention excellent in stability and bearing rigidity disclosed in Japanese Patent Laid-Open No. 2003-322146 includes a hydrodynamic radial air bearing unit having a shaft, a thrust disk attached to the shaft so as to extend perpendicularly to the shaft, and a cylindrical sleeve capable of rotating relative to the shaft and the thrust disk and defining an annular space filled with air as a working fluid together with the shaft; and a hydrodynamic thrust oil bearing unit having the thrust disk, and the cylindrical sleeve defining a space filled with an oil as a working fluid together with the thrust disk. The diameter of the hydrodynamic thrust oil bearing is greater than that of the hydrodynamic radial air bearing.
Electrical connection of a rotational member and a stationary member of an air bearing suitable for high-speed rotation is an important technical subject. An invention disclosed in Japanese Patent Laid-Open No. 2000-329141 intended to connect electrically a rotational member and a stationary member at all times for the conduction of static electricity generated in the rotational member to the stationary member fills up a space between the rotational member and the stationary member, around the axis of rotation where the rotational speed of the rotational member relative to the stationary member is the lowest or in a region where a gas necessary for generating hydrodynamic pressure for a bearing is neither sucked nor discharged, with a magnetic fluid.